Planetary systems in the foreground of the Galactic Bulge form a class of
(planetary) binary lens systems that can be detected through photometric
microlensing experiments. An Earth mass planet orbiting a lensing star can
perturb the would-be single lens microlensing light curve due to the lensing
star, briefly but spectacularly. Gravitational microlensing is the only known
ground-based method to probe earth mass planets orbiting around
main sequence stars. (Earth mass objects orbiting a neutron star
were discovered in 1992 by Wolszczan and Frail.)

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The Galactic Bulge (Dec: -30&deg) can be best observed from Southern Hemisphere
observatories in South America, Australia, and South Africa (Lat: -30&deg) or
even in Antarctica. Planetary binary lensing is rare and the planetary
signals are fairly brief -- with the lower mass planets generating
rarer and the shorter planetary signals. Thus, "microlensing planet
patroling" requires continuous coverage of microlensing alert events,
and the three continents are more or less optimally distributed for
this purpose. The South Pole offers the possibility of continuous monitoring
during the Southern winter (when weather permits). (The
top of this map has the same longitude as this web server, 273.8&deg.)

The Microlensing Planet Search Project (MPS) searches for evidence of extra-solar
planets using the gravitational microlensing technique. Photometric microlensing
is capable of probing the entire mass range of planets from Super-Jupiter mass
to Earth mass. The figure above shows an example of a microlensing lightcurve
which shows evidence for an Earth mass planet as a brief deviation in the lightcurve.
The universality of gravity gurantees that gravitational microlensing is also
sensitive to unbound planets ("rogue planets") or brown dwarfs.
(One conventional thought is that planets are formed through
accretion and brown dwarfs are formed through fragmentation during star formation.
Abundant statistics of microlensing planets can provide an important clue to test
this scenario.)

Microlensing Events

The following is a list of current and recent microlensing events that
have shown interesting deviations from standard microlensing which have
been observed or analyzed by the MPS group.

MACHO 98-SMC-1 . The critical data for this
event has come from MACHO/GMAN
observations from the CTIO 0.9m telescope. The analysis and caustic crossing
prediction for this event have been done with the binary lens fitting code
developed for the MPS project.

MACHO 97-BLG-41

MACHO 97-BLG-38

MACHO 97-BLG-28

MACHO 97-BLG-26

MACHO 97-BLG-24

MACHO 96-BLG-3 This event predated the MPS Project, but it was the first
binary microlensing event for which a caustic crossing was successfully
predicted. This was done with an early version of the MPS binary lens
analysis code.

MPS Related Papers

The following is MPS related work by collaboration members. Some of it
is theoretical: